Fix doc wrong related with substring which can be pushed down now

[xzhangxian1008]

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[hfxsd]

/merge

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This pull request has been accepted and is ready to merge.

Commit hash: d50b16a

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #13688.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.6: #13689.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.0: #13690.

[ti-chi-bot]

In response to a cherrypick label: cannot checkout release-7.1: error checking out release-7.1: exit status 1. output: error: pathspec 'release-7.1' did not match any file(s) known to git